1. Field of the Invention
The present invention relates to a method of inactivating polymers adhered to an inner surface of a reacting furnace or the like in a polycrystalline silicon manufacturing device.
Priority is claimed on Japanese Patent Application No. 2008-085671, filed Mar. 28, 2008, the content of which is incorporated herein by reference.
2. Description of Related Art
A manufacturing device employing Siemens method is known as a polycrystalline silicon manufacturing device. In the polycrystalline silicon manufacturing device, a number of silicon seed rods are arranged in a reacting furnace. The silicon seed rods in the reacting furnace are heated and raw material gas including mixed gas of chlorosilane gas and hydrogen gas is supplied to the reacting furnace to come into contact with the heated silicon seed rods. On a surface of a silicon seed rod, polycrystalline silicon produced by a hydrogen reduction reaction and a thermal decomposition reaction of the raw material gas represented by the following reaction formulas (1) and (2) is precipitated.SiHCl3+H2→Si+3HCl  (1)4SiHCl3→Si+3SiCl4+2H2  (2)
However, in exhaust gas produced by the reactions, silicon tetrachloride which is a by-product, unreacted chlorosilane gas, silicon powders, polymer compounds including Si2Cl6, Si2H2Cl4 and the like, hydrogen gas and hydrogen chloride gas are included. Among them, the polymer compounds are cooled in exhaust gas piping and the reacting furnace having a jacket structure and are thus precipitated on inner circumferential surfaces of the piping and the reacting furnace. The polymers easily ignite upon exposure to air, and thus it is required to inactivate the polymers.
In the past, a method described in, for example, Japanese Patent No. 2818780 was employed as a method of inactivating the polymers. In this method, chlorosilane such as SiCl4 is injected into piping for an exhaust gas path in a polycrystalline silicon manufacturing device and the adhered polymers are dissolved and removed by the chlorosilane.
However, since this method uses the chlorosilane, it is required to strictly handle and manage the chlorosilane so as not to expose it to air. When the remaining SiCl4 is exposed to air, safety hazards including the generation of a large amount of hydrochloric acid gas may occur.